Not all melanomas are created equal. That's the conclusion of a study by University of North Carolina researchers who found that skin cancers can vary in lethality depending on where they start.
After analyzing an exhaustive dataset of over 50,000 cases of melanoma in the US that were diagnosed between 1992 and 2003, the scientists, led by Dr. Nancy Thomas, a dermatologist, discovered to their surprise that patients with lesions in the scalp and neck died almost twice as fast after diagnosis as those whose tumors started anywhere else on the body. "The results really did surprise us," says Thomas. "For a long time, there has been a lot of controversy over whether all head and neck melanomas had worse survival, and this study shows a large difference in survival for scalp and neck tumors." Interestingly, cancers of the face and ear, other common locations for melanoma, were not linked to reduced survival. In fact, cancers starting in these areas actually had better prognosis than those beginning in the trunk or extremities, which usually have the best survival rates.
Thomas' study was not designed to tease out why these scalp and neck lesions are particularly dangerous, but she notes that those areas are crisscrossed with extensive lymph and blood vessels such networks can make it easier for cancer cells to both grow and spread. Dr. Vijay Trisal, a cancer specialist at City of Hope National Medical Center in Los Angeles, also notes that these areas receive the most sun exposure. "The maximum sun exposure areas are to the scalp, face and neck," he says, "so it makes sense biologically that cancers here would be different from those in areas that rarely see sunlight."
Thomas also acknowledges that at least part of the reason for the worse survival could be related to the fact that scalp lesions are harder to detect, and less likely to be screened, given that in most cases, the region is covered with hair. But even this can't explain the entire trend. "There is something independent of the screening that is going on that we don't really understand at this point," Thomas says.
But even without such an explanation, the findings highlight the importance of proper screening. As part of any skin exam, say Thomas and Trisal, the scalp should be no different than any other part of the body; in fact, as this study shows, they should probably be the first place doctors and patients look.